1. Field of the Invention
The present invention relates to an anode using a carbon material as an anode active material and a secondary battery.
2. Description of the Related Art
In recent years, the size and the weight of portable electronic devices such as a mobile phone, a PDA (personal digital assistant), and a notebook computer have been aggressively decreased. As part thereof, an improvement of the energy density of a battery, in particular, a secondary battery as a power source for the portable electronic devices has been strongly demanded.
As a secondary battery to provide a high energy density, for example, a secondary battery using lithium (Li) as an electrode reactant has been known. Specially, a lithium ion secondary battery using a carbon material capable of inserting and extracting lithium for the anode has been widely and practically used. However, in the lithium ion secondary battery using a carbon material for the anode, the technique has been already developed to the level close to the theoretical capacity. Thus, as a means for further improving the energy density, it has been considered that the thickness of the active material layer is increased and thereby the ratio of the active material layer in the battery is increased and the ratios of the current collector and the separator are lowered as described in Japanese Unexamined Patent Application Publication No. 9-204936, for example.